The B. henselae Immunofluorescence Assay (IFA) is used to detect antibodies to B. henselae in human serum. Infections with B. henselae have been associated with Cat Scratch Disease, bacillary angiomatosis, peliosis hepatis, and bacteremia. Titers rise during the first two-to-four weeks of illness and decline over the next six-to-12 months. In patients with previously high titers, the presence of only IgG titer of less than 160 may indicate a resolving infection. If the IFA is negative but the clinical symptoms are present, PCR testing is suggested.

B. henselae is most often transmitted to humans by cats. Recently, it has been suggested that B. henselae can also be present in the same species of tick that transmits pathogens causing Lyme disease, Babesiosis, and Ehrlichiosis. Therefore, patients with positive titers should also be tested for the other tick-borne diseases.

Principle: The B. henselae IFA assay is a two-stage sandwich assay, based upon an antigen-antibody-complex formation involving the following steps:

1. Binding of anti-henselae-specific antibodies in human serum to fixed B. henselae on a slide
2. Binding of fluorescent-labeled anti-human IgG/IgM antibodies specific to the human anti B. henselae antibodies bound to fixed henselae on the slide
3. Identifying green fluorescing henselae organisms with a fluorescent microscope

Stage of Disease: Early Disease, Late Disease

Test Methodology: IFA